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A trend toward using high-forage diets to help lower feed costs is continuing among northeastern U.S. dairies, say two researchers who have studied the practice.

Diets containing more than 55-60% forage – even up to 80% – can also maintain high milk production, utilize nutrients efficiently and contribute to herd health, says Heather Dann, a research scientist with The Miner Institute, Chazy, NY.

She and Larry Chase, Cornell University animal scientist, offer several suggestions on how to successfully transition herds to higher-forage rations.

"One of the key things to make high-forage diets work is having proper forage inventory management," Dann says. The rations generally require 15-40% more tonnage, and producers may need two or three years to adjust crop rotations, figure out how much acreage is needed and switch hybrids or varieties in order to buid adequate inventories.

“Some of the hybrids are going to be more digestible and may be lower-yielding, so taking that into account when you factor in acres is critical,” she adds.

For the past six or seven years, Chase has been observing and surveying dairies that feed forage-dominant rations. At this point, he’s tracking more than 30 herds that have switched.

Many are using conventional or brown midrib (BMR) corn silage as their major forage with legume or perennial grass silage. BMR usually offers higher digestibility than most conventional corn silage. “But people are using other feeds and doing quite well also,” Chase says.

Grass-based high-forage diets can work, Chase and Dann say, but grasses have lower rates of digestion than corn silage-based diets. They are “viable options” grown on ground not suited for silage corn or alfalfa.

Targeting quality rather than type of forage to cow groups at different lactation stages allows producers to make the most of their forages, Dann says. She suggests that they segregate feeds as they’re harvested and stored, then have them analyzed for their chemical makeup and digestibility.

“We need to target our higher-digestible forages to our fresh and early lactation cows. Forages harvested outside the optimum window can be targeted to lower-producing groups, dry cows or heifers.”

To ensure quality forage, it has to be properly harvested and stored, Dann says. Producers are usually forced to step up their production practices, Chase adds.

“Any variation in forage quality is going to be magnified because you have a bigger quantity of forage,” he says. “It does force producers to pay closer attention to potential changes in forage quality because, if they don’t, they can get bigger ups and downs in intake and milk.”

As with any ration, high-forage diets need to be balanced to adequately meet the animals’ needs, Dann says.

“The great thing is, there’s a lot of flexibility in formulating these diets. Typically, they are around 27-30% neutral detergent fiber (NDF), but quite often they’re going to be a bit higher, 30-35%. They’re going to have a minimum NDF from forage of 19-21%, but when we formulate diets with highly digestible corn, such as BMR, it’s going to be higher, usually 23-28%,” the researcher points out.

Producers should make sure diets contain enough physically effective fiber. “When feeding high-corn silage diets, we need to process that corn. Quite often, you might need to include 1-2 lbs of straw when you feed high levels of BMR corn silage. Otherwise, you’re going to have sub-acute ruminal acidosis, even in a diet that has 65% forage.”

Generally, cows are healthier on high-forage diets, according to farmers Chase has studied. “The general observation is that it does improve herd health. There are fewer acidosis problems, and cows do stay in the herds longer.”

Before switching to the new diets, producers should check that their TMR mixers can handle higher volumes of forages. If they’re at capacity, loads won’t mix well and could contribute to increased sorting, intake variation and other issues at feeding, Dann says. “This is a great time to implement a TMR audit,” which checks ration consistency.

Producers should also see how the new diet could affect feedbunk management and cow behavior, Dann mentions. Because heifers and first-lactation animals eat slower than mature cows, more bunk space may be needed or the cows may need to be fed more often.

“What it really comes down to is watching cows and adjusting the diets as needed. It’s critical to track milk and intake so you can monitor efficiency,” she says.